Adjustable transmission line



July 23, 1946.

S. B. PICKLES ADJUSTABLE TRANSMISSION LINE Filed May 12, 1942 2 Sheets-Sheet l LNVENTOR SIDNEY B. Plexus flZJ/Z 1/4 ATTORNEY July 23, 1946. s.. B. PICKLES ADJUSTABLE TRANSMISSION L-INE FiledMay 12, 1942 2 Sheets-Sheet 2 ATTORNEY Patented July 23, 1946 I ADJUSTABLE TRANSMISSION LINE Sidney B. Pickles, Jackson Heights, N. Y.,' assignor l j to FederalTelephone and Radio Corporation, j' I a corporation of Delaware Application May 12, 1942, Serial No. 442,657

16 Claims.

This invention relates to transmission lines and more particularly to a phasing unit therefor by which the effective length of an electrical line can be varied.

In the type of phasing unit heretofore commonly used, the lines were telescopingly coupled and phase adjustment made by trombone action. This type of phasing unit, however, is objectionable because it is clumsy and awkward to use and a the adjustment is not smooth. Further, the diflO ferences in diameter of the, cooperating telescoping parts of this type of unit efiect discontinuities in the surgeimpedance so that reflections occur.

Bearing in mind the aforementioned disadvantages of the trombone type of phasing unit, it is 15 an object of this invention to produce a phasing unit for electricallines which is'compact, easily operated, and in which the operating effect is smooth.

Another object of the invention is to produces- 20- tionary arcuate segments of conductor materialfi' one end of each segment having means for-connection to an electrical line, and locating rotatable conductor means betweentthe stationary segments for sliding engagement therebetween,

so that upon rotation ofthe conductor means,

theefiective length of the electricalline is varied.

More particularly, the arcuate segments may be disposed in oppositely opposed pairs about a given axis and a movable member mounted for rotation about the givenaxis to ,movably support conductors extending crosswise between the oppositely opposed segments. The ends of the movable conductors'have brushes, each of which conductively engages one of the arcuate segments. member, the brushes of the movable conductors are moved along the arcuate segments thereby increasing or decreasing, as the case may be,- the lengths of the electrical lines. 1

The arcuate segments may be suitably shielded by a casing which has a. cylindrical portion extending adjacent and in spaced relation to the segments. Likewise, the'movable conductors are provided with a shield disposed 'in'a like spaced relation adjacent thereto. g

In order to minimize the influence of portions of the arcuate segments extending beyond the points at which the conductor means engage the segments, the free ends of the arcuate segments are shorted or grounded to the shield. In addi- Thus, by rotationof the supporting tion to shorting the free ends of the segments, a movable arm may be carried by the rotating member and provided with brushes to short the adjacent arcuate segments'at a given distance from the brushes of the movable conductor means. The arm may be made adjustable relative to the supporting member so that the shorting effect thereof can be adjusted'for a distance from the point of conductor engagement with the segments equal to substantially one-fourth of the wave length of the current carried by the; elec trical lines. Thi movable short gives an ,open effect to the free ends and insures against-the otherwise free end portions-of the segments pro ducing reflections or influencing the phasing effect ofthe unit. Thus, a the effective lengths of the electrical lines are changed by manipulation'of the rotary member, the movableshorting arm is moved therewith so as, to short the arcuate segments at-rsubstantially one-.fourth wave length of the current carried by the lines and-thereby eliminate any reflections onphasing effect that the terminal end portions of the segment might otherwise impose upon the lines. Thisinvention may be applied to coaxial cables as well as plural line installations. In the case of coaxial cables the free end portions of the segments are shorted to the casing or shield of the unit in substantially the same manner as here inbefore described. That i to say, the free; or terminal ends of the segments are ,conductively connected to the casing and movable shorting brushes are disposed between the segments and the shield for movement one-fourth of a wavelength beyond the brushes of the movable conductor. v For a betterunderstanding of the invention, reference may be had tothe following detailed description to be readin connection withthe drawings, in which v v r v Fig. 1 is a plan View of one embodiment of this invention, with the top portion thereof removed; Fig. 2 i a vertical cross-sectional view taken along line 2-2 of Fig. 1; I I

.Fig. 3 15 a cross-sectional-view taken along line 33 ofFig.2; w

Fig. 4 is avertical cross-sectional viewtaken along line 4--4 of Fig. 1; and

Fig. 5 is a schematic view. of anotherembodi-l ment of the invention. 1 I

Referring to Figs. 1, 2, 3 and 4 of the drawings,

.the embodiment of the invention therein illustrated comprises a cylindrical casing or shield 10 having top and bottomportions l2 and I4 respectively. The top portion I! has secured thereto' thereto a boss I8.

3 a boss 55 and the bottom portion [4 has secured Supported in the bosses l6 and I8 are stub shafts 20 and 2| respectively, to

'which diametrically-extending arms 22 and 23 are adjustably secured by suitable clamps 24 having tightening elements 26. These arms 22 and 23 are joined at both ends by cross-straps 6| integral therewith-thus forming a generally rectangular frame whose purpose is hereinafter explained. An inner shield 30 of flat rectangular form is provided with supporting extensions '32 and 34 integral thereto and extending atTr'ight'i angles as shown in Fig. 3. The upper supporting extension 32 is received overthe 'stubf shaft 201 and the lower extension 34 is 'received'on the stub. shaft 2| The extension 32 is clampedbetween the arm 22 and a flanged sleeve '35- carried by i 4 conductors 52 and 53, this being in turn connected to a third section of line comprising the active portion of the pair of segments 4| and 43 (i. e.-

" the above. described composite line at the points Where the first and third sections join the second section-l :If these stub sections were not controlled they might have such length as to present low or fairly low impedances to the composite line thus; causing large or fairly large reflect ions.

the shaft 20. The extension 34is likewise clamped between the arm 23 and a flanged sleeve 36.

Mounted in spaced relation to the cylindrical shield l-O are two pairs of oppositel disposed arcuate conductor segments 40, 4'2 and" 4!; 43. As shown i-n Fig. 1, each arcuate segment is supported at one end by a metallic block 44- thereby grounding that end of the segment tothe shield I0. At suitably spaced intervals,- each segment may be further supported by insulators '46 to maintain it in properly spaced relation to the shield. To avoidaltering the size and cross:

section of the cond'uctors; the insulators 46 are' secured thereto by screws .41 the flat heads of V which are'solder'ed to the surfaces of tl'ieconductors." The end of each segment oppositethe end groundedtelthe shield lil'is suitably connected to lead of a cable 48 or '49 to which'atrans-* missionor; otherelectrical line mayfbe connected.

The two shields'l'fl and 30 arepreferably made of the same materialand have substantially the same thickness.

; Hi. The mountings 5-8 (Fig. 3;) between the conductors 5-2, 53 and the insulators 59 5! arethe same; as thefinsulated supporting mounts for the arcuatesegments (Fig. 2).' The conductors 52 v and 'ti3 -are straight and extend along the diameter of, the circle which includes the arcuate segments. The ends of the conductors52 anq -53 are provided with brushes 5'6; 56' and 51, 51f respectively for resilient engagement with thearcuate segments, As shown in Figs. 1 and'Z 'the brushes-56, 56" ,of'the conductor 52 are engagement with the'segments 40 and 4| and the brushes 51 of the'conductor 53 are in engagement with the segments 42 and 43. i V,

The shaft is provided witha suitable handle '60- so that the shaft 20', theassociated shield and the conductors 52,53 may be readily rotated in either directio n by manipulation of the handle. By turning the handle to the right'or'left as desired, the effective length of the composite transmission line formed by conductors 52'ancl V 53 and the active portions of the arcuate seg-.

ments may be lengthenedor. shortened, 'as the case may be. This composite line maybe con-' sidered a consisting of a first section of line comprising the active portion of the-pai-roi seg- "ments 40 and "(i."e, the portion shownbetweenv cable '48 and brush 5B*in;Fig. 1) connected to a second section of line comprising the Whole of For the purpose of preventing the unused or free end portions of the arcuate segments from acting as substantial impedances shun-ted across.

this line, and thus causing reflections, the cross traps 6| of arms 22' and 23 are provided with brushes 62 and 64 (Fig. 3) each ofwhich is adapted to engage a pair of the arcuate segments of the two pairs 40, 42 and'4l, 43 As shown, the brush 62 engages segments 4| and" 43 while'the brush 64' engages both of the segments '40 and 42 thereby shorting the segments; The distance of the shorting brushes 62 and 64 from the conductive engagement of the segments by the conductors 52, 53 maybe changed depending uponthe frequency of the current carried by the :transmission line. This adjustment, as hereinbefore suggested, may be made by loosening the elements 26' and moving the arms 22, 23 to the-desired angula-rrelation/with respect to the fconductors 52, 53. The distance between the brushes 62,64 and the brushes 56, 56, 5T, 51 as measured along the segments, is preferably selected as one-fourth of the Wave length of the; frequency of the current of the transmission line. This relation, effectively renders practically infinite the. bridged impedances constituted by the unused or deadend portions of thearcuate segments.

From the foregoing, it will be readily'apparent that the effective length of the composite electrical line may be readily and easily changed by simple manipulation of the handle ,60. For each rotary movement of the. handle, the position of the conductors 52, 53 will'b'e changed so that the ingly. Simultaneously with this movement, the

' arms 22 and 23 will move to maintain a shorting connection between adjacent arcuate segments at a distance substantially one-fourth wave length beyond the location of the brushes 56, 51 of the movable conductors. 1 n

The provision of the'inner shield 3 0' adjacent the movable conductors 52, 53 insures the maintenance of asurge impedance'for these conduc tors which corresponds to the surgeimpedance of the arcuate segments with their" shield ID. This uniformity of surge ,impedance along the composite line together with the elimination of any substanti-al bridged impedances due to the unused or free ends results in avoiding reflections to a greater. degree than any known'type of ad-/ .5 blocks 13. One end of each segment is connected to the innerconductors 14 of two cable sections while the casing is connected to the outer portions of the coaxial cable. The other 1 ends of the. segments are shorted by conductive connection to the casing by metallic blocks 16.

Any suitable rotary member .11 may be mounted on the casing to movably support a conductor 18. This conductor is provided with brushes 19 for conductive engagement with the two segments. By turning the rotary-member, the effective length of the composite line interconnecting the two inner conductors l tmay be varied. v Y I The rotary member 'ILmay also} be provided with arms 80 and 8| each having brushes 83 and '84 for sliding engagement with one or the seg- As described in connection with the first embodiment, a shield 85 having brushes 85 for conductive engagement with the casing H is provided for movement, the spacing of conductor 18 therefrom being the same as the spacing of segments 10, 12 from the casing II. This spacing may be less than the spacing between inner and outer conductors of the high frequency coaxial cables 15 in order to yield the same surge impedance as that of the cables. Alternatively the conductors 10,12 and 78 may be of larger diameter than conductors 14 or may be of flat cross-section so as to yield with one-sided shielding the same surge impedance as the conductors 14 which are shielded on all sides.

While two embodiments of the invention have been shown and described, it will be readily apparent to those skilled in the art that many changes, variations and adaptations thereof are possible without departing from the invention.

It will be understood, therefore, that the foregoing illustration and description is to be regarded as illustrative of the invention only and not as a restriction upon the appended claims.

What is claimed is:

1. A phasing unit comprising stationary arcuate segments of conductor material, a shield disposed adjacent said segments and forming therewith a length of line having a predetermined surge impedance, a rotatable member, conductor means movable with said member and having sliding engagement with said segments, and a second shield disposed adjacent said conductor means and rotatable with said member said second shield forming with said conductor means a length of line having a surge impedance substantially equal to said first mentioned surge impedance.

2. A phasing unit comprising stationary arcuate segments of conductor material, one end of each segment being connectable to an electrical line having a given surge impedance, a shield disposed adjacent said segments and forming therewith a length of line having substantially the same surge impedance as the surge impedance of said electrical line, a rotatable member, conductor means movable with said member and having sliding engagement with said segments, and means to short the other ends of said segments to said shield. I

3. A phasing unit comprising stationary ar cuate segments of conductor material, a shield disposed adjacent said segments, a rotatable member, conductor means movable with said member and having sliding engagement with saidsegments, means movable with said member to short saidsegments to said shield at a distance from the points of sliding engagement by said conductor means, and said distance being equal to a portion of" the wavelength of the current carried by. said lines. a

'4. A phasing unit comprising stationary arcuate-segments of conductor material, one end of each segment beingconnectableto an elec- *trical line, a shield disposed adjacent said segments, a rotatable member; conductor'means movable with said member and having sliding engagement with said segments, means to conductive'ly connectthe other ends ofsaid segments to said shield,'means movable withsaid member to short said segments to said shield, means to maintain the shorting means at a distance from the points of the sliding engagement of said conductor means, and said distance being equal to substantially one-fourth of the wavelength of the current carried by the electrical lines.

5. A phasing unit comprising stationary arcuate segments of conductor material, a shield disposed adjacent said segments, a rotatable member, conductor means movable with said member and havingsliding engagement with said segments, means movable with said member to short said segments to said shield, and means for adjusting theangular relation between the shorting means and said conductor means so that thedistance between the shorting means and the points of said sliding engagement may. be

V at one end of each segment to connect the segchanged for currents of different frequencies.

6. A phasing unit comprising two pairs of 'stationary arcuate segments of conductor material in'opposite'ly disposed co-axial relation, means ment to an electrical line, the other ends of the adjacent segments of the two pairs being con- 45: nected together, a rotatable member co-axial with said segments, and conductors rotatable 'withsaid member, each of said conductors extending radially in opposite directions from said member and being so disposed as to provide conduction' between'one segment of each'of said pairs,

7. A phasing unit comprising two adjacent pairs of oppositely disposed stationary arcuate segments of conductor material, a rotatable member, conductors movable with said member, each conductor being so disposed as to provide conduction between the segments of one of said pairs, means movable with said member and slidably engaging the adjacent segments of the two pairs at a distance beyond the points of conduction between said conductors and said segments, and

said distance being a predetermined portion of the wavelength of the current carried by the segments.

8. A phasing unit comprising two adjacent pairs of oppositely disposed stationary arcuate segments of conductor material, a rotatable member, conductors movable with said member, each conductor being so disposed as to provide conduction between the segments of one of said pairs, means for shorting the segments of the adjacent pairs, and means to adjust the location of the shorting means relative to said conductors.

disposed stationary arcuate segments of conrductor material, a shield di posed adjac nt th 7 segments of said is tsrone end of each s me being connectable to an electrical line, the other ends of the adjacent segments being connected o ether, a m vabl member, condu t rs m va with .said member, each conductor :being so disposed as to provide conduction between the two opimsite segments of one of said sets, and a secondsnield disposed adjacent said conductors and movable with said member,

' 10,. The phasing unit defined inclaim' 9 charaoterized by the'fact that, the spacingbetween the first-mentioned shield and i m t n V the'spacing between said second shield and said conductors are substantialiythe same.

11 1. A phasing unitcomprising two ad acent sets of se ments each set comprising two oppositel-y I disposed stationary arcuate segments of eonductor-inateiial, means at one end ofeach segment to connect the segment to an electrical,

line,';a shield disposed adjacent said segments,

means conductively connecting the other ends of the segments of said sets together, a movable member, conductors movable with said member,

each conductor being so disposedas to provide conduction between the two opposite segments of one of said sets, and a shield disposed adjacent said conductors. 1

12. A phasing unit comprising two adjacent sets of seginents each set comprising two oppositely' disposed stationary arcuate segments of conductor, material, means at one end of each segment to connect the segment to a transmission line, a shield disposed adjacent saidsegments, ,means conductively connecting'the other,

ends of the segments of said sets together, a movable member, conductors movable with said member, each conductor being so disposed as to prowas asing, one end of eacnsegment being conduc tively connected to said casing, a member,means to rotatably support said member coaxially of said casing, a conductor carried by said member and having sliding engagement with said two segments, and an arm connected :to said memher having sliding engagement with said segments to electrically connect the segments at a distance beyondthe sliding engagement between said conductor and said segments-. 7

1,4. A phasing unit, comprising 'a cylindrical casing, two adjacent sets of segments each set comprising twov oppositely; disposed arcuate segments supported in spaced relation to said casing, said casing having top and bottom portions, each of. said portionsghavingya stub shaft rotatably mounted therein, the shafts being coaxial, apiece ment with said segments, and an arm adjustably supported on one of the shafts and having, sliding engagement with adjacent segments of the two sets to electrically connect the segments at a distance beyond the sliding engagement leevide conduction between the segments of one of a a said sets, a shield disposed adjacent said conductors, and means movable with said member and slidably engaging the adjacent'segments of the two sets at a distance beyond the points of conduction between said conductors and said segments, and said distance being substantially equalto one-fourth of the wave-length of the ourrent carried by the segments. v 13. A phasing unit comprising a cylindrical casing, at least two arcuate segments, means to support the segments in spaced relation to said ment.

tween said conductor and said segments equal to,

a predetermined fraction of the wavelength of thercurrent carried by said segments, 1, I

15,. A phasing unit for adjustingthe electrical length of a transmissionrline comprising line section extensions, one end of each section being adapted for connection to part of said line, the other ends of said extensions being free, conductive connecting means therefor adjustable alongthe lengths of said extensions, conductive shields in parallel relation with said extensions and with said connecting means and co-operating therewith to constitute lines whose surge impedance simulatesthe surge impedance of the line being adjusted.

'16. A phasing unit according to claim 15, in-

eluding means under the control of the adjustable connecting means for preventing the free ends of the line extensions from affecting the impedance of the transmission line under adjust- 'SIDNEY B. PICKLES; 

